An underground steam explosion tore through a Manhattan street near Grand Central Terminal on Wednesday, sending edgy residents running for cover amid a plume of steam and flying rubble, and causing brief panic about another terror attack.

Officials said at least one person died because of the explosion. Several people were injured, at least four of them seriously.

New York Police Department spokesman Paul Browne said the explosion was not terrorism.

"There is no reason to believe whatsoever that this is anything other than a failure of our infrastructure," Mayor Michael Bloomberg said at a news conference at the scene of the blast. Bloomberg said it is possible cold water from the morning rain entered the steam pipe, causing the explosion. It is feared possible that asbestos was also released into the air, the mayor said.

Sixteen people were taken to Bellevue Hospital, including the person who died, said spokesman Stephen Bohlen. He said two seriously injured patients were being treated in the hospital's trauma unit. The remainder suffered minor injuries, he said.

Two people who were seriously injured were being treated at New York Weill-Cornell Medical Center. They were in critical condition, said hospital spokeswoman Emily Berlanstein.

Many Metro-North commuters found alternative routes back home to Westchester and the Hudson Valley, incorrectly believing Grand Central Terminal was closed.

"It was open," said New Rochelle resident Franklin Brown, who ended up avoiding the train Wednesday evening. "We had to go through the 47th Street and Madison entrance, but we didn't know that at the time."

Metro-North told commuters to expect a normal morning commute Thursday.

Information from the Associated Press was used in this report.

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